Carburetor



M. C. BROWN Feb. 16, 1965 CARBURETOR Filed Oct. 31, 1962 M M 1 5L5..- 2

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N mw m B C B R R O M AGENT 3,170,006 I CARBURETOR Morris C. Brown, St. Louis, Mo, 'assignor to ACF Industries Incorporated, New York, N.Y., a corporation of New Jersey Filed'Oct. 31, 1962, Ser. No. 234,393 Claims. (Cl. 261-459) This invention is directed to a. carburetor for small engines used in various types of installationssuch aswith power tools, gocarts, etc.

A type of carburetor utilized with small engines fitted to power tools is one having a closed fuel chamber so that fuel can be provided to the carburetor and engine in all positions of the power tool. Many tools utilizing small internal combustion engines-are controlled by a triggeroperated throttle, which normally has an off throttleclosed position, at which the engine operates at low speed, and an on throttle-open position, at which the engine is operated at high speeds. The trigger is connected to the carburetor throttle so that the operator merely pulls the Unit States, a eto i e] trigger from the off position to the on position to speed up the engine from a low speed operation to the high speed or work condition.

Certain engine driven'tools,. such as a power saw require that the speed-up of the engine occurs rapidly upon the opening of the throttle from the low speed position to the highspeed position. This acceleration of the engine must of necessity be very rapid with no pausing or stumbling of the engine as it develops high speed; The demands on the carburetor are thus such that the engine acceleration be substantially instantaneous by providing an immediate flow of high speed flow of fuel to the engine in response to the fast opening of the carburetorv throttle.

It is thus an object of this invention to provide means by which the carburetor will respond instantaneously to the full opening of the throttle to provide sufiicient fuel for almost instantaneous acceleration of an engine.

It is a further object of thisinvention to provide a nozzle structure in which, upon rapid opening of the throttle of the carburetor, an instantaneous response occurs to provide a large supply of fuel and air adequate for high speed operation of the engine.

The invention is directed to a novel nozzle construction in which a fuel well encloses one portion of the nozzle, the other end of which extends into the mixture passage of the carburetor. A pair of air bleeds extend from the mixture conduit upstream of the nozzle into the fuel well to provide an air flow into the fuel well, when the carburetor throttle is opened. This flow of air emulsifies some of the fuel in the fuel well as well as lifts the available solid fuel up through the nozzle into the mixture conduit. This action provides a rapid flow of fuel to the engine in response to the sudden flow of air through the carburetor due to the opening of the throttle valve.

FIGURE 1 is a longitudinal sectional view of a carburetor, in accordance with the invention, connected to an engine.

FIGURE 2 is a sectional view laterally of the carburetor structure of FIGURE 1.

FIGURE 3 is a partial sectional view of a portion of the carburetor of FIGURES 1 and 2 showing the low speed circuit of the carburetor.

FIGURES 4 and 5 are partial sectional views of the nozzle structure in accordance with modifications of the invention.

' FIGURE-1 shows a carburetor 10 incorporating the invention and connected to an engine E partially shown in the figure. The carburetor 10 consists substantially of a tubular body member 11 having a longitudinal passageway 12 extending therethrough, in alignment with an opening 14 into the engine E. The opening 14 may be I 3,176,006 Patented Feb..16, 1965.

a portion of the intake manifold of a four cycle engine or may consist ofa portion of the engine crankcase of a two cycle-engine. At the other end of the passage 12. from the engine there is mounted an air filter 16 consisting of a sheet metal annularhousing filled with an air filacross the passage 12 when in its closed position shownin FIGURE 1. To rotate the throttle 2% between an open and'a closed position, the throttle is mounted on a shaft 22 journaled in the wall of the tubular conduit 12 and having one end 24 (FIGURE 2) extending outwardly of the carburetor, to which is attached an operating lever 26 for throttle operation. Between the throttle 2t and the air filter 18 and within the air horn section 27 of conduit 12, there is mounted a circular choke valve structure 2 8, which is fixed for movement to a choke shaft 3%} also journaled in the wall of the conduit 12. A small aperture 28a is formed through the plate of valve 23 to provide some air for-starting. Manual means are also provided for opening and closing the choke valve 28 when desired. This manual means is not shown in the figures but may be of any well known and conventionalstructure. Betweenthe choke shaft 39 and the throttle shaft 22, the

. mixture conduit 12 is formed with a restricted portion having a venturi surface dilwhich provides a throat or constriction of the conduit 12 and which is also provided with a flaring skirt portion 32 between the venturi surface 30 and the downstream end of the conduit 12.

A fuel chamberit ir is provided below the mixture conduit 12, as shown in FIGURES 1 and 2. The fuel chamher is formed between a recess 35 in the body 11 of the carburetor and a flexible diaphragm 36 stretched across the recess 35 and sealed around its periphery by the rim of a cap structure 38 fixed to the carburetor'body by machine screws it as indicated. A fiber washer 42 is fitted between the rim of cap 33 and the periphery of the diaphragm 36. To the center of the diaphragm 36 are fixed a pair of backing plates 44, which are fastened together with the diaphragm inbetween by a rivet 46. Between the diaphragm assembly and the cap 38 is an air chamber 48 to provide control of the diaphragm 36. An aperture 4-5 through cap 38 connects the air chamber 48 to the atmosphere.

Fuel is delivered into the fuel chamber 34 from a fuel tank or reservoir 5-0 schematically indicated in FIGURE 2 through an inlet line 52 connected to one end ofan inlet fitting 54. The other end of fitting 54 joins to an inlet fuel chamber 56 of a fuel pumping structure closed by an inlet valve 58. A pumping chamber on is separated from a pulsation chamber 62 by a pump diaphragm 64. The pulsation chamber 62 is connected by an ai'r passage 66, shown in dotted lines in FIGURE 1, to the intake mani fold or crankcase of the engine B through the opening 14.

During engine operation pulsations within the crankcase or manifold are transmitted through passage 66 to the chamber 62 for operating the pump diaphragm 64. Fuel is thus drawn into the pump chamber 60 and then out through an outlet check valve 68 into connected passages 7tland '72. i A portion of fuel passage 72 is controlled by a needle inlet valve 74 having a pointed end operating against a resilient valve seat 76 to control the flow of fuel from the pumping chamber 66) into the fuel chamber 34. The inlet valve 74 is operated in a closed direction by a coil spring 78 axially mounted around the valve 74 and pressing the pointed end of the valve onto the seat 76. The spring 78 is mounted between a flanged end of the valve74, as shown in FIGURE 2, and a portion of a fitting 80 enclosing the valve 74-. The lower end of the valve 74 is formed with a nail head 82 into which a bifurcated end of a lever 84 is fitted. The lever 84 is fulcrumed on a pin 86 mounted within the body cavity 34. The other end of lever 84 rests against the rivet 46 of the diaphragm assembly.

The high speed circuit of the carburetor consists of a recess 88 extending from the fuel chamber 34 into the body 11 of the carburetor to a cross passage 90, in which is threaded an adjustment needle 92. Needle 92 has a tapered end 94 extending into a restricted passage 95 between the bore 90 and a fuel well 96 drilled into the body 11 and separated from the fuel chamber 34 by a disk 98 press-fitted into the body 11. Restricted passage 95 may have an inside diameter of 0.052 inch. A tubular nozzle structure 100 is fitted through the wall of the mixture passage 12 separating it from the fuel well 96. One end of the tubular nozzle 100 extends through the venturi surface 30. The other end of the tubular nozzle extends into the well 96 to a point closely adjacent to the separating disk 98. The inside diameter of the tubular nozzle may be 0.040 inch. Nozzle tube 100 is provided with several small apertures 101 through the side wall.

A low speed circuit of the carburetor is shown specifically in FIGURES 1 and 3 and consists of a recess 102 connecting the fuel chamber 34 with a cross passage 104, in which is threaded a low speed control needle 106. In a manner similar to the control needle 92, needle 106 has a tapered end 108 extending into a restricted passage 110 connecting the cross passage 104 with a low speed fuel well 112. Restricted passage 110 may have an inside diameter of 0.035 inch. Well 112 is separated from the fuel chamber 34 by a press-fitted disk 114. As shown in FIGURE 1, an idle port 116 extends from the low speed fuel well 112 into the mixture passage 12 downstream of the throttle in its closed position. A second idle air port 118 connects the idle fuel chamber 112 with the mixture conduit upstream of the closed position of throttle 20.

In operation, turning over the engine E provides a suction within the engine manifold or crankcase, which tends to draw air through the air filter 18 down the mixture passage 12. The choke valve 28 is closed and the throttle valve 20 is opened during cranking of the engine. Air flows through the aperture 28a in the choke valve 28. The low pressure or manifold vacuum downstream of the closed choke 28 will provide a suction or low pressure in the nozzle 100, which is reflected through the fuel passages to provide a sub-atmospheric pressure in the fuel chamber 34. Atmospheric pressure against the underside of the diaphragm 36, as viewed in FIGURES 1 and 2, will press the diaphragm upwardly to open valve 74 and permit fuel to enter the fuel chamber 34. The fuel is then sucked through the recess 88, passage 90 into the fuel well 96 and through the nozzle 100. Fuel will also flow through the low speed system through recess 102, passage 104 and into the idle well 112 and out the idle ports 116 and 118. Air sucked through the mixture passage will mix with this fuel to provide an enriched starting air and fuel mixture for the engine. 7

After the engine starts, the choke valve 28 is opened and the engine operates at low speed with the throttle in the closed position shown in FIGURE 1. The mixture passage in the region of the venturi 30 is now substantially at atmospheric pressure so no fuel is urged through the nozzle 100. However, low pressure in the mixture passage 12 downstream of the closed throttle 20 will continue to suck fuel out of the idle port 116. 'Idle air will flow through the port 118 into the idle well 112 to mix with this fuel to provide air and fuel mixture sufiicient for low speed operation of the engine. The optimum amount of fuel flow out of the port 116 is obtained by the adjustment of needle 106.

Upon opening of the throttle 20 to a full open position, air will flow rapidly through the mixture passage in response to the engine. At the venturi restriction 30 the air flow will provide a low pressure region so that fuel will be urged out of the nozzle 100 by atmospheric pressure on the diaphragm 30. The amount of fuel for optimum high speed engine operation is obtained by the adjustment of the high speed needle 92.

During operation of the engine, the subatmospheric conditions in the region of the venturi 30 or at the idle port 116 are reflected in the fuel well 34, which keeps the fuel in chamber 34, at a subatrnospheric pressure. This permits atmospheric pressure on the lower side of the diaphragm 36 to press the diaphragm inwardly against the bias of spring 78 to rotate the lever 84 in a clockwise direction, as viewed in FIGURE 2, to retain the valve 74 open. During low speed operation, since the flow of fuel out of the idle port 116 is relatively small, the opening of the valve 74 is to a much less degree than during high speed operation of the engine when a greater amount of fuel flows through the main nozzle 100. During either operation of the engine, however, the diaphragm and needle assembly occupy a substantially static or equilibrium position at which the fuel flow past the valve 74 into the fuel chamber 34 equalsthe flow of fuel out of the chamber 34 into either the high speed circuit or the low speed circuit of the carburetor.

In accordance with the invention, the metal cap or plug 98 between the fuel chamber 34 and the high speed fuel well 96, has a small restricted passage 119 of a predetermined size connecting the fuel chamber to the fuel well 96. The size of the restricted passage 119 is selected to provide a flow of fuel slightly less than that required for operation of the engine at high speed. In this manner then the adjustment needle 92 can be positioned so that the point 94 is well within the restricted passage and the adjustment of the needle will be in the nature of a vernier adjustment which is less critical than when all fuel flow is through passage 95 during high speed operation.

Also, in accordance with the invention, means are incorporated in the carburetor which provide a rapid acceleration of the engine upon a sudden opening of the throttle 20. As pointed out above, the carburetor is of the type used with power tools and often with a trigger control for the throttle 20. In such applications, the operator desires the engine to operate either at a low speed which is around 2000 r.p.m. or at a high power speed around 6500 r.p.m. Accordingly, merely pulling the trigger opens the throttle from a closed position to a wide open position and permits the engine to operate at high speed. It is desirable in applications of this type that the engine have immediate acceleration. For example, in the use of such engines with chain saws, the throttle is immediately moved from closed to wide open position on pulling the manual trigger. Immediate acceleration of the engine should occur and usually with a simultaneous application of a load. This requires that if the load is applied during theengine speed-up from low speed to high speed that it will not stall out. Thus, it is necessary that there be an immediate response in the flow of fuel to the engine to prevent the engine from stumbling or stalling.

Therefore, in accordance with the invention, an air bleed system is used to instantaneously force fuel out of the nozzle into the mixture passage upon the sudden opening of the throttle 20. The air bleed, as shown in FIGURE 1, is provided by a passage 1120 extending from the top of the fuel well 96 to the mixture passage 12 upstream of the nozzle 100. A small restriction 122 is placed within the bleed passage 120 and is selected to provide the desired optimum flow of air into the well 96. Restriction 122 is calibrated with an inside diameter of between 0.020 inch to 0.035 inch. In high speed engine operation, air under higher pressure upstream of the venturi surface 30 will tend to flow through the bleed passage 120 into the fuel well 96. This air will quickly be sucked with fuel through the 55 r apertures 101 of nozzle 1%. i This action serves to emulsify the fuel in nozzle and lighten "it as well. The air bled in nozzle 1% also accelerates the fuel-outwardly throughQnozzle 100 into the mixture passage 12. This provides an instant flow of fuel in the passage 12 for the rapid acceleration of the engineuponvopening ai /6,066 r high speed engine operation, and an adjustably movable needlelmounted in said body and extending into the other one of said predetermined restrictions'to control the opening therethrough to provide additional fuel to said fuel well required forhigh speed engine operation.

2. A carburetor comprising a body, a fuel and air mixture conduit through said-body, said body formed with-a fuel chamber, a fuel inlet and a fuel conduit extending from'said fuel inlet to said fuelchamber, an'

to provide the optimumfiow of air into the fuel well 7 120 and 124 are utilized. This structure provides a combined effect, in which the air bleed 120 provides an emulsification of the fuel to lighten it and provides quick acceleration into the tubular nozzle 100, while the bleed passage 124 provides air which lifts the fuel upwardly quickly through the tubular nozzle 190 and out into the mixture passage 12. Thiscombination of air bleeds 120 and 124 together with the tubular nozzle construction 100 provides an accelerating structure which is effective to provide instant acceleration of the engine upon rapid opening o-fthe throttle.

The restriction 119 in the plate 98, as well as the Vernier passage between the high speed adjusting needle 92 and the restriction passage 95 are sufficiently small, that during low speed operation, when there is no fuel flow through the nozzle 100, fuel will be retained within the fuel well 96, in spite of the fact that there is a differential of pressure between the end of the nozzle in the mixture passage 12 and the pressure of the fuel in chamber 34. These close spacings prevent any back bleeding of air through the nozzle 100 into the fuel chamber 34 during low speed operation of the engine. Furthermore, they insure that the well 96 is retained full of fuel during low speed operation so that upon sudden opening of the throttle 20 fuel is present to be pressed by the air flow through the bleed passages out the nozzle 100 and thus provide the required engine acceleration.

I claim:

1. A carburetor comprising a body, a fuel and air mixture conduit through said body, said body formed with a fuel chamber, a fuel inlet and a fuel conduit extending from saidfuel inlet to said fuel chamber, an inlet valve in said fuel conduit between said fuel inlet and said fuel chamber, means for operating said inlet valve, said operating means including a diaphragm operatively connected to said inlet valve and sealed at its periphery to said body across said fuel chamber to form a wall thereof, said body having a fuel connection between said fuel chamber and said mixture conduit, said fuel connection including a fuel well adjacent to said mixture conduit, a tubular nozzle fitting fixed within said fuel connection and having one end extending into said mixture conduit and another open end enclosed within and spaced from the wall of said fuel well, a pair of fuel passages in said body extending between said fuel chamber and said fuel well, each one of said fuel passages having a different fixed predetermined restriction therein, one of said fuel passages formed of a size to supply fuel to said fuel well at a rate less than that required for inlet valve in said fuel conduit between "said fuel inlet and said fuel chamber, means for operating said inlet valve, said operating means including a diaphragm operatively connected to said inlet valve and sealed at its periphery to said body across said fuel chamber to form a wall thereof, said body having a fuel connection between said fuel chamber and said mixture conduit, said fuel connection including a fuel well adjacent to said mixture conduit, a tubular nozzle fitting fixed within said i fuelco'nnection and having one end extending into said mixture conduit and another open end enclosed within and'spaced from the wall of said fuel well, said fuel connection including a pair of fuel passages in said body extending between said fuel chamber and said fuel well, means forming a separating wall between said fuel well and said fuel chamber, an aperture through said separating wall forming one of said fuel passages and formed of a size of supply fuel to said well at a rate less than that required for high speed engine operation, and adjustable restriction means for varying fuel flow through the other one of said fuel passages to provide additional fuel to said well required for high speed engine operation.

3. The invention of claim 2 including first air bleed passage extending from a point in said mixture conduit upstream of said nozzle into said fuel well at a point adjacent to an intermediate portion of said fuel nozzle, and a second air bleed passage extending from said mixture conduit upstream of said fuel nozzle into said fuel well adjacent to the enclosed open end of said fuel nozzle, said tubular nozzle fitting having a plurality of apertures through the Wall and extending along the length thereof within said fuel well.

4. A carburetor comprising a body, a fuel and air mixture conduit through said body, said body formed with a fuel chamber, a fuel inlet and a fuel conduit extending from said fuel inlet to said fuel chamber, an inlet valve in said fuel conduit between said fuel inlet and said fuel chamber, means for operating said inlet valve, said operating means including a diaphragm operatively connected to said inlet valve and sealed at its periphery to said body across said fuel chamber to form a wall thereof, said body having a fuel connection between said fuel chamber and said mixture conduit, said fuel connection including a fuel well adjacent to said mixture conduit, a tubular nozzle fitting fixed Within said fuel connection and having one end extending into said mixture conduit and the other end enclosed within and spaced from the wall of said fuel well, said fuel connection including a pair of fuel passages in said body extending between said fuel chamber and said fuel well, means forming a separating wall between said fuel well and said fuel chamber adjacent to the enclosed end of said fuel nozzle, said separating wall formed with an aperture aligned with the axis of said tubular fuel nozzle, said aperture forming one of said fuel passages and formed of a size to supply fuel to said well at a rate less than that required for high speed engine operation, and adjustable restriction means for varying fuel flow through the other one of said fuel passages to provide passage between said fuel inlet and said fuel chamber, means for operating said inlet valve, said operating means including a diaphragm operatively connected to said inlet valve and sealed at its periphery to said body across said fuel chamber to form a Wall thereof, said body having a fuel connection between said fuel chamber and said mixture conduit, said fuel connection including a single fuel well adjacent to said mixture conduit, a tubular fuel nozzle fixed Within said fuelconnection and having one end opening into said mixture conduit and another open end enclosed within and spaced from the wall of said fuel well, a first air bleed passage extending from a point in said mixture conduit upstream of said nozzle and directed downwardly into said fuel Well and terminating at a point adjacent to said enclosed open end of said fuel nozzle to entrain air into the fuel entering the enclosed open end of said nozzle to lift said fuel through said nozzle upon opening of said throttle, said tubular nozzle having a plurality of apertures through the Wall thereof and extending along the length thereof Within said fuel well, and a second air bleed passage extending from a point in said mixture conduit upstream of said nozzle into said fuel Well at a point between the ends of said nozzle and adjacent to said apertures to entrain additional air through said apertures to emulsify fuel within said nozzle upon opening of said throttle.

References Qited in the file of this patent UNITED STATES PATENTS Smith Apr. 23, 

1. A CARBURETOR COMPRISING A BODY, A FUEL AND AIR MIXTURE CONDUIT THROUGH SAID BODY, SAID BODY FORMED WITH A FUEL CHAMBER, A FUEL INLET AND A FUEL CONDUIT EXTENDING FROM SAID FUEL INLET TO SAID FUEL CHAMBER, AN INLET VALVE IN SAID FUEL CONDUIT BETWEEN SAID FUEL INLET AND SAID FUEL CHAMBER, MEANS FOR OPERATING SAID INLET VALVE, SAID OPERATING MEANS INCLUDING A DIAPHRAGM OPERATIVELY CONNECTED TO SAID INLET VALVE AND SEALED AT ITS PERIPHERY TO SAID BODY ACROSS SAID FUEL CHAMBER TO FORM A WALL THEREOF, SAID BODY HAVING A FUEL CONNECTION BETWEEN SAID FUEL CHAMBER AND SAID MIXTURE CONDUIT, SAID FUEL CONNECTION INCLUDING A FUEL WELL ADJACENT TO SAAID MIXTURE CONDUIT, A TUBULAR NOZZLE FITTING FIXED WITHIN SAID FUEL CONNECTION AND HAVING ONE END EXTENDING INTO SAID MIXTURE CONDUIT AND ANOTHER OPEN END ENCLOSED WITHIN AND SPACED FROM THE WALL OF SAID FUEL WELL, A PAIR OF FUEL PASSAGES IN SAID BODY EXTENDING BETWEEN SAID FUEL CHAMBER AND SAID FUEL WELL, EACH ONE OF SAID FUEL PASSAGES HAVING A DIFFERENT FIXED PREDETERMINED RESTRICTION THEREIN, ONE OF SAID FUEL PASSAGES FORMED OF A SIZE TO SUPPLY FUEL TO SAID FUEL WELL AT A RATE LESS THAN THAT REQUIRED FOR HIGH SPEED ENGINE OPERATION, AND AN ADJUSTABLY MOVABLE NEEDLE MOUNTED IN SAID BODY AND EXTENDING INTO THE OTHER ONE OF SAID PREDETERMINED RESTRICTIONS TO CONTROL THE OPENING THERETHROUGH TO PROVIDE ADDITIONAL FUEL TO SAID FUEL WELL REQUIRED FOR HIGH SPEED ENGINE OPERATION.
 5. A CARBURETOR COMPRISING OF A BODY HAVING A FUEL AND AIR MIXTURE CONDUIT THERETHROUGH, A THROTTLE VALVE IN SAID MIXTURE CONDUIT, SAID BODY FORMED WITH A FUEL CHAMBER, A FUEL INLET AND A FUEL PASSAGE EXTENDING FROM SAID FUEL INLET TO SAID FUEL CHAMBER, AN INLET VALVE IN SAID FUEL PASSAGE BETWEEN SAID FUEL INLET AND SAID FUEL CHAMBER, MEANS FOR OPERATING SAID INLET VALVE, SAID OPERATING MEANS INCLUDING A DIAPHRAGM OPERATIVELY CONNECTED TO SAID INLET VALVE AND SEALED AT ITS PERIPHERY TO SAID BODY ACROSS SAID FUEL CHAMBER TO FORM A WALL THEREOF, SAID BODY HAVING A FUEL CONNECTION BETWEEN SAID FUEL CHAMBER AND SAID MIXTURE CONDUIT, SAID FUEL CONNECTION INCLUDING A SINGLE FUEL WELL ADJACENT TO SAID MIXTURE CONDUIT, A TUBULAR FUEL NOZZLE FIXED WITHIN SAID FUEL CONNECTION AND HAVING ONE END OPENING INTO SAID MIXTURE CONDUIT AND ANOTHER OPEN END ENCLOSED WITHIN AND SPACED FROM THE WALL OF SAID FUEL WELL, A FIRST AIR BLEED PASSAGE EXTENDING FROM A POINT IN SAID MIXTURE CONDUIT UPSTREAM OF SAID NOZZLE AND DIRECTED DOWNWARDLY INTO SAID FUEL WELL AND TERMINATING AT A POINT ADJACENT TO SAID WELL ENCLOSED OPEN END OF SAID FUEL NOZZLE TO ENTRAIN AIR INTO THE FUEL ENTERING THE ENCLOSED OPEN END OF SAID NOZZLE TO LIFT SAID FUEL THROUGH SAID NOZZLE UPON OPENING OF SAID THROTTLE, SAID TUBULAR NOZZLE HAVING A PLURALITY OF APERTURES THROUGH THE WALL THEREOF AND EXTENDING ALONG THE LENGTH THEREOF WITHIN SAID FUEL WELL, AND A SECOND AIR BLEED PASSAGE EXTENDING FROM A POINT IN SAID MIXTURE CONDUIT UPSTREAM OF SAID NOZZLE INTO SAID FUEL WELL AT A POINT BETWEEN THE ENDS OF SAID NOZZLE AND ADJACENT TO SAID APERTURES TO ENTRAIN ADDITIONAL AIR THROUGH SAID APERTURES TO EMULSIFY FUEL WITHIN SAID NOZZLE UPON OPENING OF SAID THROTTLE. 